We have continued our studies on the alterations of transfer RNA populations of hepatomas and fetal liver. Earlier reports from our laboratories have indicated that the elution profiles of histidyl, asparaginyl and tyrosyl tRNAs from fetal liver exhibit a marked shift to higher salt concentrations as compared to the same respective aminoacyl tRNAs from adult liver. These preliminary findings obtained by methylated albumin kieselguhr column chromatography have been confirmed with the more sensitive system of reverse phase chromatography. No changes in the elution profiles of lysyl and phenylalanyl tRNAs of fetal liver have been observed. We are extending these studies to other aminoacyl tRNAs of fetal liver and and also exploring the nature and function of the multiple species in the aminoacyl tRNAs of tyrosine, histidine and asparagine. We are also continuing our investigations on the biological functions of polyamines, and the new developments suggest that the polyamines mediate the stimulation of messenger RNA synthesis in inducible systems (i.e., Beta-galactosidase induction) through an initial translational event.